Myasthenia gravis in pregnancy and birth: identifying risk factors, optimising care J. M. Hoff a , A. K. Daltveit b,c and N. E. Gilhus a,d a Section for Neurology, Department of Clinical Medicine, Bergen; b Section for Epidemiology and Medical Statistics, Department of Public Health and Primary Health Care, University of Bergen, Bergen; c Medical Birth Registry of Norway, Bergen; and d Department of Neurology, Haukeland University Hospital, Bergen, Norway Keywords: delivery, myasthenia gravis, neonatal myasthenia gravis, pregnancy, thymectomy Received 29 November 2005 Accepted 7 March 2006 Women with myasthenia gravis (MG) have increased risk of pregnancy complications and an adverse pregnancy outcome. This study examined risk factors for such com- plications in order to improve the care for pregnant MG women. Through the Medical Birth Registry of Norway, 73 MG mothers with 135 births were identified. Their obstetrical and clinical records were examined. Data on pregnancy, delivery and the newborn were combined with information on mother’s disease. The risk for neonatal MG was halved if the mother was thymectomized (P ¼ 0.03). Children with neonatal MG were more likely to display signs of foetal distress during delivery (P ¼ 0.05). Only in one-third of the pregnancies did the patient see a neurologist during preg- nancy. These patients used MG medication more often during pregnancy (P ¼ 0.001), and were more likely to be thymectomized (P ¼ 0.007). They also had a higher rate of elective sections (P ¼ 0.009). Thymectomy may have a protective effect against neo- natal MG. Neonatal MG can cause foetal distress during delivery. Most MG women benefit from being examined by a neurologist during pregnancy, to minimize risks and select the best delivery mode in collaboration with obstetricians. Introduction Early onset of Myasthenia gravis (MG) with thymic hyperplasia, high acetylcholine receptor (AChR) anti- body concentration and no other muscle antibodies, is the dominant MG subtype amongst women in fertile age [1]. Pregnancy does not worsen the long-term out- come of MG, but the disorder sometimes becomes manifest during pregnancy or postpartum [2,3]. The first trimester and the postpartum period represent the most critical phase for exacerbations [4]. Myasthenia gravis is associated with an increased rate of both complications and operative interventions during delivery [5]. The complication rate is increased also in asymptomatic MG [6]. Transplacental trans- mission of IgG antibodies can lead to neonatal MG, which affects 10–20% of children born to MG mothers [2,7]. Symptoms of neonatal MG consist mainly of transient respiratory problems and difficulties in feeding and swallowing. It is important that these children are observed and treated optimally. Maternal MG is also a rare cause for arthrogryposis multiplex congenita, a congenital disorder characterized by multiple joint contractures and other anomalies, probably resulting from lack of movement in utero [8]. Both conditions can occur in offsprings of women with very little symptoms or where MG is not yet diagnosed [6,9]. In this study, we identified all MG mothers who had given birth in Norway during the last 36 years. Detailed obstetrical and clinical records were collected for 135 births in 73 women. Data on pregnancy, delivery and the newborn were combined with information regard- ing mother’s disease in order to identify factors responsible for the increased complication rate. Material and methods Medical Birth Registry of Norway The Medical Birth Registry of Norway (MBRN) was established in 1967 and is based on the compulsory notification of all births in Norway after 16 weeks of gestation. The notification form is sent within 9 days after birth or discharge from the hospital. The registry contains data on the mother’s demographic variables, the pregnancy, the delivery and the newborn. The registry is placed under the Norwegian Institute of Public Health. The MG-diagnosis in MBRN Diseases of the mother, both before and during preg- nancy, are recorded on the birth notification form and Correspondence: Dr Jana Midelfart Hoff, Section for Neurology, Department of Clinical Medicine, Haukeland University Hospital, University of Bergen, 5021 Bergen, Norway (tel.: +47 99427605; fax: +47 55975165; e-mail: jana.midelfart.hoff@helse-bergen.no). 38 Ó 2006 EFNS European Journal of Neurology 2007, 14: 38–43 doi:10.1111/j.1468-1331.2006.01538.x